The invention relates to a surgical method for expanding a vertebral canal of a vertebra of the spine, also called laminoplasty.
The vertebral canals of the vertebrae of the spine form the so-called canalis vertebralis or spinal canal in which the spinal cord, enclosed by the spinal meninx, is located.
The spinal cord as part of the central nervous system may be prevented from functioning properly if, for example, with the occurrence of spinal canal stenosis, pressure is exerted on the spinal cord. This may have several causes, for example, the existence of spondylosis or ossification of the posterior longitudinal ligament.
This may be remedied by enlargement of the vertebral canal of the vertebra or vertebrae of the spine that is or are affected so that the spinal cord has more space available and can therefore evade the pressure.
An overview of the therapeutic options commonly used to date can be found, for example, in F. Meyer et al., Deutsches Ärtzeblatt, year 105, issue 20, pages 366 to 372. In addition to the ventral methods, various dorsal methods, namely laminectomy with and without fusion and laminoplasty, are used. Ventral methods may also be used in combination with dorsal methods.
Of the various dorsal methods, laminoplasty works with the least surgical interventions in the bone substance.
To date, various laminoplasty operating techniques have been proposed. The two most important of these are described in the literature as so-called single-door or double-door techniques. An overview of these and an assessment of the effects to be expected with regard to pressure relief and expansion of the spinal canal is, for example, to be found in the publication by Wang, Xiang-Yang et al. in SPINE, Vol. 31, No. 24, 2006, pages 2863 to 2870.
In the so-called single-door technique, also called open-door technique, the lamina is split on one side of the vertebra with an incision gap, whereas on the other side of the lamina a groove is made without splitting the vertebral arch.
The area of the vertebral arch with the groove acts like a hinge during the subsequent opening of the vertebral canal and allows the vertebral arch to be opened, which involves fracture of the bone substance. The vertebral arch remains joined to the vertebral body by the periosteum and the collagenous fibers of the bone substance.
In the so-called double-door technique, the spinous process of a vertebra is split or completely removed and a groove is made in the lamina on both sides of the spinous process, with the areas of the vertebral arch containing the grooves again acting as hinges. The vertebral canal is now opened by swinging apart the two vertebral arch sections with the associated spinous process parts, if still existing, and the bone substance in the area of the hinges likewise fractures. Here, too, the vertebral arch sections remain joined to the vertebral body by the periosteum and the collagenous fibers of the bone substance.
With both techniques, the vertebral canal of the vertebrae is fixed in the opened state by implants. In addition to the body's own bone chip, an hydroxyapatite spacer or the like is used as implant material.
In spite of the reduced surgical intervention in the bone substance in comparison with other dorsal methods, a significantly increased rate of subsequent neck pain is still regarded as a disadvantage of laminoplasty, as is restricted mobility of the cervical spine, which is often observed.